Modern engines utilize an electronic engine control module (ECM) to continuously monitor and control engine operation to optimize fuel economy, emissions control, and performance. The ECM uses various physical sensors to collect information reflecting current operating conditions. The information is used to generate output signals for various actuators which control operation of the engine. Using the actuators, the ECM controls the air-fuel ratio, fuel injection, ignition timing, and various other functions to control operation of the engine. Optimal control of the engine over a wide range of engine operating conditions (and ambient conditions) depends on the availability, accuracy, and reliability of data gathered by the engine sensors.
An ideal engine control system would be capable of directly measuring each engine operating parameter which affects any control variable. However, any realizable design is subject to considerations such as the cost, durability, repairability, and/or technological feasibility (including packaging considerations) of appropriate sensors. The deployment of more and more physical sensors results in per-unit cost penalties in development and manufacturing. Replacement and repair costs also rise due to the increased number of sensors and difficulty in diagnosing sensor malfunctions. As such, actual systems typically involve design compromises to accommodate technological difficulties and reduce the cost and complexity of the physical system employed to monitor and control the engine. It is therefore desirable to improve the availability, accuracy, and reliability of data used to effect engine control without significantly impacting the cost, complexity, or repairability of the vehicle.